Single crystals such as silicon carbide, sapphire, silicon (Si), and germanium (Ge), and ceramics such as alumina, zirconia, ferrite, and silicon nitride are hard brittle materials that cannot be cut but are processed by grinding or polishing work.
There have been devised methods for grinding or polishing hard brittle materials with use of particles of diamond or cubic boron nitride (CBN). In addition, methods for cutting such materials through heating with laser light or the like have been also attempted. However, these cutting methods using laser light are addressed for glass materials, hard-to-cut metal materials, and the like, but are not suited for hard brittle materials. Nevertheless, with the advancement of laser techniques in recent years, there have been increasingly proposed cutting methods for cutting hard brittle materials while softening the materials by heating with laser light.
For example, Non-patent Document 1 described later discloses that ceramic 101 (silicon chloride and partially-stabilized zirconia) is cut by 1500 watts of carbon dioxide laser light 100 as illustrated in FIG. 7. Non-patent Document 1 also reports a method for cutting a material by cubic boron nitride (CBN) as a cutting tool 102 under processing conditions with a cutting speed of 1 to 2 mm/sec and a cutting depth of 0.5 to 1 mm.
Patent Document 1 described later discloses a cutting method by which the focus of laser light 104a, 104b is adjusted to the surface of a material to be cut 105 placed at a distance of approximately 1 to 10 μm from the blade edge of a cutting tool 103 in the direction of forward movement as illustrated in FIG. 8, the laser light 104a, 104b is incident to the material to be cut from the top, and an irradiated part 105a irradiated with the laser light 104a, 104b is softened as illustrated in FIG. 9 and then cut.
Patent Document 2 described later discloses a cutting method by which a cutting tool 106 (for example, diamond) that can transmit laser light with an emission wavelength used (for example, YAG laser light of 1060 nm) is used as a waveguide for laser light to propagate the laser light and apply the laser light from the blade edge of the cutting tool 106 directly to the surface of a material to be cut 107.